Methods and systems for efficient separation of polarized uv light

ABSTRACT

Methods and systems are provided for separating polarized UV light. In one example, a method may include passing polarized source light through a first prism, the polarized source light including desired light and undesired light, separating the desired light from the fundamental light, and passing the separated desired light through a second prism. The separated desired light which is passed through the second prism may then be further passed through a spatial filter.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 62/668,096, entitled “METHODS AND SYSTEMS FOR EFFICIENT SEPARATIONOF POLARIZED UV LIGHT,” filed on May 7, 2018, the entire contents ofwhich are hereby incorporated by reference for all purposes.

FIELD

The present description relates generally to methods and systems forseparating polarized UV light.

BACKGROUND AND SUMMARY

Separation of light may desirable for a wide range of applications. Forexample, separation of light at particular wavelengths may be desirablefor spectroscopy and chromatography, among other applications where alight source at a particular wavelength may be desirable, such as curingand research applications, for example. In applications related tospectroscopy and chromatography, pure extraction of light at a desiredwavelength may be important for obtaining accurate measurements.

In the application of generating UV light emission from a visible lightsource using the second harmonic generation (SHG) principle, desired SHGlight is approximately collinear with undesired fundamental light, wherethe fundamental light is residual light at a fundamental wavelength ofthe visible original pump light source. An intensity of the fundamentallight may be several orders of magnitude higher than that of the desiredSHG light due to a low SHG conversion efficiency at low irradiancelevels, including UV irradiance levels. Such low SHG conversionefficiency at the low irradiance levels makes it difficult toeffectively separate the desired SHG light from the undesiredfundamental light.

For example, the high intensity of the fundamental light relative to theSHG light may result in diffraction of the fundamental light within alight separating device such as a spatial filter and lead to incompleteseparation of the desired SHG light from the fundamental light. It isnoted that the desired SHG light may be UV light in one or moreexamples.

Spectral filters for separation of UV light have traditionally reliedupon the use of specialized materials with a high UV transmission andhigh refractive index contrast to separate UV light. However, theinventors have recognized several issues with such traditional spectralfilters for performing UV light separation.

For example, there are few materials that have both a high enough UVtransmission and a high enough refractive index contrast to perform UVlight separation, and the materials meeting both the high UVtransmission and high refractive index requirements for UV lightseparation are costly. Such costly materials and requirement ofsophisticated filter design lead to increased manufacturing costs forspectral filters, especially with regards to traditionalhigh-performance spectral filters for light separation in a deep UVwavelength range (e.g., lower than 300 nm), where a thin film-basedfilter is often utilized. In some cases, traditional custom filters maycost tens of thousand dollars to design and fabricate.

Moreover, traditional spectral filters filtering light at deep UVwavelength often yield poor results due to a low transmission efficiencyof the desired SHG light in a pass band or a low attenuation of theundesired light in the rejection band. For example, some filters mayhave lower than 20% transmission of the desired UV light and can onlyreject 99% of undesired fundamental light (e.g., equivalent to havingOptical Density of 2, OD2).

Thus, recognizing these above issues, the inventors have developed anapproach to separating UV light that achieves high performance polarizedUV light extraction via prism refraction and spatial filtering. Via theapproach developed by the inventors, highly effective UV lightextraction may be achieved with cost savings compared to traditionalspectral light filtration.

In one example, the issues described above may be addressed by a methodfor passing polarized source light through a first prism, the polarizedsource light including second-harmonic generation (SHG) light andfundamental light, separating the SHG light from the fundamental light,and passing the separated SHG light through a second prism. The SHGlight passed through the second prism may then be further passed througha spatial filter in one or more examples to further reduce scatteredstray light.

In this way, substantial spatial and spectral separation between desiredlight (the SHG light) and undesired light (the fundamental light) may beachieved for efficient desired light extraction, while avoiding the useof costly materials. The throughput of SHG light as high as 99.7% andthe attenuation of the fundamental light higher than OD8 has beenobserved.

As one example, optics included in a light separation system may providepolarized source light, the source light comprising desired SHG lightand undesired fundamental light. It is noted that the source light maybe visible light in one or more examples. The polarized source light maythen be directed through the first prism, and the first prism mayrefract the source light causing some separation of the desired light,such as SHG light, and the undesired light, such as fundamental light.However, the amount of spatial separation created via the first prismmay not be sufficient for extraction of the desired light withoutpollution from the undesired light due to diffraction from the spatialfiltering. Thus, the desired light is further passed through a secondprism following refraction at the first prism to create further spatialseparation from the undesired light. Via the methods and systemsdeveloped by the inventors, desired SHG light may be separated fromundesired fundamental light in order to enable efficient extraction ofthe desired SHG light. Moreover, the approach developed by the inventorsmay be at greatly reduced cost compared to traditional approaches whichmay have required specialized materials or inefficient gratings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a first example light separationsystem, according to at least one example of the present disclosure.

FIG. 2 shows a schematic diagram of a second example light separationsystem, according to at least one example of the present disclosure.

FIG. 3 shows a schematic diagram of a third example light separationsystem, according to at least one example of the present disclosure.

FIG. 4 shows a plot of a percentage of transmission of SHG light vs.incident angle (θ).

FIG. 5 shows an example method, according to at least one embodiment ofthe present disclosure.

FIG. 6 shows a schematic diagram of a fourth example light separationsystem, according to at least one example of the present disclosure.

DETAILED DESCRIPTION

The following description relates to systems and methods for separationof polarized UV light. In at least one example light separation system,two or more prisms may be positioned relative to a polarized sourcelight such that the source light may be separated into desired light andundesired light.

For example, such an example light separation system may include twoprisms, such as shown at FIG. 1 . Alternatively, an example lightseparation system may include more than two prisms, such as shown atFIG. 3 , where the light separation system shown at FIG. 3 includesthree prisms. Additional prism stages may be used if even higher degreeof separation is desired.

In one or more examples, the light separation system of the presentdisclosure may include a spatial filter positioned downstream of theprisms in a path of the desired light for further filtration purposes.The spatial filter may be a pinhole, as shown at FIG. 2 , for example.Thus, as shown in the method at FIG. 5 , polarized source light may beseparated via filtration through two or more prisms, and, in at leastone example, a spatial filter. Such an approach may beneficially achievehigh performance separation of light without having to utilize costlymaterials found in traditional spectral filters, for example. In one ormore examples, the light separation system of the present disclosure maybe contained within a case in order to block environmental light foraccurate readings, such as shown at FIG. 6 .

For purposes of discussion, FIGS. 1-6 will be described collectively.Thus, elements described introduced in a first figure may not bereintroduced in subsequent figures and may be labeled similarly.

Turning to FIG. 1 , FIG. 1 shows a first example light separation system100. As shown in FIG. 1 , the first example light separation system 100includes optics 102, where optics 102 generate source light 104.

The optics 102 may be positioned upstream of a first prism 108, and asecond prism 114, where upstream and downstream is in reference to amovement of second-harmonic generation (SHG) light through the lightseparation system 100.

Optics 102 may generate source light 104, where the source light 104 maybe visible light in at least one example. For example, optics 102 maygenerate a laser source light 104. The source light 104 is polarized andcomprises SHG light 110 as well as fundamental light 112. In one or moreexamples, a type-I phase matching scheme may be used in the optics 102.In examples where type-I phase matching may be used in optics 102, theSHG light 110 and the fundamental light 112 of source light 104 may haveperpendicular polarization 120. The first prism 108 and the second prism114 may be oriented so that the SHG light 110 is polarized parallel tothe plane of incident and often termed as p-polarized, as shown in FIG.1 . The Fresnel equation indicates that the SHG light 110 may havetransmission as high as 99.7% through the first prism 108 and the secondprism 114, which is higher than traditional spectral filters.

In at least one example, the source light 104 may be a visible lightsource (e.g., 430 nm wavelength), such as a laser, and the source light104 may comprise SHG light 110 and fundamental light 112, where thedesired SHG light 110 is approximately collinear with the undesiredfundamental light 112 of the source light 104. The intensity of thefundamental light 112 may be several orders of magnitude higher thanthat of the desired SGH light 110 due to low conversion efficiency atlow irradiance levels.

Source light 104 generated by optics 102 may be directed through firstprism 108, and SHG light may be further directed through second prism114. First prism 108 and second prism 114 may be made of opticallytransparent material. For example, first prism 108 and second prism 114may be isosceles prisms, and first prism 108 and second prism 114 may bemade of fused silica in one or more embodiments. For example, the firstprism 108 and the second prism 114 may be two isosceles prisms made offused silica with one angle α=69 degrees.

Both first prism 108 and second prism 114 may comprise a plurality offacets 116, where the facets 116 of each of the prisms are used tointroduce a propagation angular difference between desired light 110 andundesired light 112. In at least one example, the facets 116 may becoated with a coating 128 that favors specific spectral or polarizationcontent. Such a coating 128 may beneficially be applied to the facets116 in order to adjust separation performance of the prisms, forexample. However, the light separating systems disclosed herein arehighly efficient even without coating 128. Thus, the facets 116 may beuncoated for purposes of reduced cost in at least one example, whilestill achieving highly efficient light separation.

The first prism 108 is positioned in a light path of the source light104 generated by optics 102, so that optics 102 directs source light 104through first prism 108.

The SHG light 110 and the fundamental light 112 of source light 104 areapproximately collinearly incident upon entry at a facet 116 of firstprism 108. In one or more examples, the source light 104 may becollinearly incident on a facet 116 of the first prism with an angle θof approximately 30 degrees, shown at incident angle 122 in FIG. 1 . Asdiscussed in further detail below, the transmission of the SHG light 110through a single prism may be at an angle θ=30 degrees. For example,incident angle 122 in FIG. 1 may be an angle θ=30 degrees, where the SHGhas a polarization axis perpendicular to the base of the prism resultsin efficient SHG light transmission.

The source light 104, including SHG light 110 and fundamental light 112,passed through the first prism 108 is refracted by first prism 108 andseparates SHG light 110 and fundamental light 112 of the source light104. Thus, the SHG light 110 and fundamental light 112 are approximatelycollinear upon entry into first prism 108, and SHG light 110 andfundamental light 112 exit first prism 108 at two different exit angles.

For example, the SHG light 110 and the fundamental light 112 may besubstantially collinear upon entry through first prism 108, and the exitangles of the SHG light 110 and fundamental light 112 exiting firstprism 108 may differ. In one or more examples, the difference betweenthe exit angle of the SHG light 110 and the fundamental light 112 may bebetween 1 degree and 10 degrees. It is noted that as SHG light 110 isdesired in at least one example, SHG light may also be referred to asdesired light herein. Similarly, as fundamental light 112 is undesirablein at least one example, fundamental light 112 may also be referred toas undesired light herein. In one or more examples where the sourcelight 104 may be a visible light source, the SHG light 110 may not bevisible light. For example, in cases where the light source 104 may be alaser (e.g., 440 nm wavelength), the SHG light 110 may be UVC lightemission (e.g., 220 nm wavelength) separated from the visible lightsource.

Due to the small angular difference between the SHG light 110 andfundamental light 112 upon exiting the first prism 108, substantialpropagation space following refraction of the source light 104 via thefirst prism 108 may be required for successful separation to occur, aslight exiting first prism 108 has an extended Gaussian beam profile witha significantly larger intensity of fundamental light 112 compared tothe SHG light 110. That is, the difference of the exit angles betweenthe SHG light 110 and the fundamental light 112 achieved by a singleprism is not sufficient for performing high efficiency light separationwithout substantial propagation space, as the extended Gaussian beamprofile of the fundamental light 112 may result in residual fundamentallight 112 extending into the light beam of desired SHG light 110.Moreover, the inclusion of a spatial filter (e.g., a pinhole)immediately following the first prism 108 may also fail to achieveseparation between desired SHG light 110 and fundamental light 112, as astructure defining the spatial filter opening may diffract fundamentallight into the spatial filter opening.

However, the second prism 114 is positioned in a path of SHG light 110,and out of a path of fundamental light 112. Thus, after exiting thefirst prism 108, the SHG light 110 passes through second prism 114 andthe fundamental light 112 does not pass through the second prism 114 inthe geometric optical sense. That is, a significant portion of the beamof the fundamental light 112 does not pass through the second prism 114after being passed through the first prism 108, and a beam of thedesired light 110 (e.g., SHG light) is passed through the first prism108 and then passed through the second prism 114. In at least oneexample, the significant portion of the beam of fundamental light 112that does not pass through the second prism 114 may be more than half ofthe beam of fundamental light 112. In another example, the significantportion of the beam of fundamental light 112 that does not pass throughthe second prism 114 may be more than 75% of the beam of fundamentallight 112. Such passing of the desired SHG light 110 through secondprism 114 may beneficially combat a diffraction effect due to theGaussian geometry of the fundamental light beam by steering fundamentallight 112 far away from the second prism 114, and thus also steerfundamental light 112 away from SHG light 110. The fundamental light 112may be directed to a fundamental light receiver 138, in one or moreexample. For example, fundamental light receiver 138 may be a light dumpto absorb the fundamental light 112 and prevent pollution of the desiredSHG light 112. Additionally or alternatively, the fundamental lightreceiver 138 may comprise one or more sensors for referencing purposes.For example, the fundamental light receiver 138 may comprise one or moresensors for reference against light received at detector 126 formeasurement purposes.

Though not shown, the system may further include additional prismsdownstream of the first prism 108 through which only the fundamentallight 112 is passed through in order to increase a spatial separationbetween the desired SHG light 110 and the fundamental light 112. The SHGlight 110 passed through second prism 114 is refracted via the secondprism 114, further physically separating desired light 110 fromundesired light 112. Put another way, via the second prism refraction ofthe desired light signal 110, the angle between desired light 110 andundesired light 112 is increased. It is noted that in one or moreexamples, the desired light 110 may be UV light, such as UVC light.However, other desire light wavelengths may be possible.

Thus, though only a small degree of separation of the desired light andthe undesired light may be achieved by passing light through the firstprism 108 which results in a system which is unable to sufficientlyseparate desired light from undesired light without substantialpropagation space, via the use of at least two prisms, substantialphysical separation of the desired light 110 from the undesired light112 may be achieved within a small space. Therefore, by refracting theSHG light 110 through both the first prism 108 and the second prism 114,the technical effect of efficient extraction of desired light may beachieved in a compact manner.

Following refraction of the SHG light 110 through second prism 114, theSHG light may then be directed to a detector 126.

For example, in cases where the light separation system 100 may be apart of a spectroscopy device or chromatography device, such as ahigh-performance liquid chromatography (HPLC) device, the SHG light 110may be directed through the first prism 108 as a part of source light104, then the SHG light 110 may be directed through the second prism116, a sample 130, and received at detector 126, where detector 126 mayprovide a reading to a control unit 132. In examples where the lightseparation system 100 is not part of a measurement device such as aspectroscopy device, however, the SHG light 110 directed through thesecond prism 116 may be directed to a destination other than a sample130 and detector 126. In particular, the SHG light 110 passed throughthe second prism 116 may then be directed towards any desired finaldestination without being passed through a sample and detector.

In at least one example, control unit 132 may be communicatively linkedwith a display unit 134. Thus, responsive to receiving the reading fromdetector 126, control unit 132 may provide an output to display unit134, such as a wireless or a hardwired output, and the display unit maydisplay the reading via display unit 134. In some examples, the displayunit 134 may be connected to the control unit 132 via a wiredconnection. However, in one or more examples, the display unit 134 maybe connected to the control unit 132 via a wireless connection. Inaddition to detector 126 sending outputs to control unit 132, it isnoted that light separation system 100 may further comprise a user inputreceiving unit 136 which is also connected to the control unit 132. Forexample, the user input receiving unit 136 may comprise one or more of atouch screen, microphone, piezoelectric receiving device, mouse,keyboard, etc. In one or more examples, all of the components of thefirst example light separating device 100 may be contained within acase. Alternatively, the optics 102, first prism 108, and second prism114 may be contained within a case, and one or more of the sample 130,detector 126, control unit 132, display unit 134, and user inputreceiving unit 136 may be contained within the case.

In cases where the first example light separation device 100 may be aspectrophotometer or chromatograph, for example, a reading may be takenresponsive to receiving a user input at user input receiving unit 136requesting a reading. For example, user input receiving unit 136 mayprovide an output to control unit 132 responsive to receiving a userinput, and control unit 132 may comprise instructions stored innon-transitory memory executable by a processor of control unit 132 to,responsive to receiving the request for a reading via an output fromuser input receiving unit 136, operate optics 102 and direct polarizedsource light 104 from optics 102 to first prism 108, where desired light110 (e.g., SHG light) is separated from undesired light 112 (e.g.,fundamental light) via refraction at first prism 108.

The desired light 112 separated from the fundamental light 110 via thefirst prism 108 may then be passed through second prism 114, creatingfurther spatial separation between desired light 112 and fundamentallight 110. The desired light 112 may then be further passed through asample 130 and received at detector 126. For example, sample 130 may bea liquid or a gas sample. The sample may be contained in a cuvette inone or more examples. The detector 126 may provide an output to controlunit 132 responsive to receiving the desired light 112 at detector 126.

Further, whereas the desired light 110 is directed towards second prism114, sample 130, and detector 126 following refraction at first prism108, the undesired fundamental light 112 may be directed towardsfundamental light receiver 138 and received at the fundamental lightreceiver 138, away from desired light 110 following refraction at firstprism 108. In cases where the fundamental light receiver 138 maycomprise one or more sensors, fundamental light receiver 138 may providean output to control unit 132 responsive to receiving the fundamentallight 112.

Further, though not shown, it is noted that in some cases one or more ofa reference sample and additional prisms may be positioned in a path ofthe fundamental light 112 between the first prism 108 and thefundamental light receiver 138. The inclusion of one or more additionalprisms in the path of the fundamental light 112 between the first prism108 and the fundamental light receiver 138 may be advantageouslyoriented to create further spatial separation between the desired light110 and the fundamental light 112 for improved purity of desired lightextraction.

The control unit 132 may comprise instructions stored in non-transitorymemory executable by a processor of the control unit 132 to displaylight measurements responsive to receiving the output from the detector126 and the output from the fundamental light receiver 138. For example,the light measurements may be displayed via a display unit such asdisplay unit 134. In some examples, displaying the light measurementsmay include displaying the raw signal data from both the fundamentallight receiver 138 and the detector 126. Additionally or alternatively,displaying the light measurements may include displaying lightmeasurements taking into account the output from the fundamental lightreceiver 138 as a reference for comparison against the output from thedetector 126.

Alternatively, however, fundamental light receiver 138 may not beincluded in the first example light separation system 100, or thefundamental light receiver 138 may absorb undesired fundamental light112 without providing an output to control unit 132.

In such examples where there is no fundamental light receiver 138 orwhere fundamental light 112 is absorbed at the fundamental lightreceiver 138 without an output being provided to the control unit 132via fundamental light receiver 138, a display may be provided based onupon the output received from detector 126 responsive to a request for areading.

Turning now to FIG. 2 , FIG. 2 shows a schematic diagram of a secondexample light separation system 200. In addition to the optics 102,first prism 108, and second prism 114 included in first example lightseparation system 100, light separation system 200 may further comprisea spatial filter 202 and a detector. In at least one example, spatialfilter 202 may be a pinhole formed into a case 206. Case 206 maysurround the optics 102, first prism 108, and second prism 114, in oneor more examples. Moreover, while control unit 132, display unit 134,and user input receiving unit 136 are shown outside of the second lightseparation system 200, any one or more of the control unit 132, displayunit 134, and user input receiving unit 136 may be positioned withincase 206.

However, in at least one example the second example light separationsystem 200 may not include a detector.

As discussed above in relation to FIG. 1 , small physical separationbetween SHG light 110 and fundamental light 112 prevents a spatialfilter from effectively separating SHG light 112 from fundamental light112. For example, if source light 104 is only passed through a singleprism and a spatial filter is positioned immediately downstream of thesingle prism, the Gaussian beam profile of the fundamental light 112 maycause the fundamental light 112 to interfere with SHG light 110 at thespatial filter. In particular, the fundamental light 112 may refract offof the structure defining an opening of the spatial filter, causing thefundamental light 112 to interfere with the SHG light 110.

However, by directing source light 104 through the first prism 108 toseparate the SHG light 110 and the fundamental light 112, and thenpassing only the beam of SHG light 110 through second prism 114, the SHGlight 110 may be further refracted by the second prism 114 and aphysical separation between the beam of SHG light 110 and the beam ofthe fundamental light 112 may be increased. The increase in spatialseparation between the SHG light 110 and the fundamental light 112 mayenable a spatial filter 202 proximal and downstream of the second prism114 to function.

That is, due to the increased spatial separation of the SHG light 110and the fundamental light 112 downstream of the second prism 114, thetechnical effect of reducing an amount of undesired fundamental light112 that is able to interfere at the spatial filter 202 is greatlyreduced. Via the inclusion of a spatial filter 202 in addition to the atleast two prisms, a significant signal rejection ratio as much as 1E8may be achieved to reduce undesired fundamental light 112. Thus,efficient separation of desired SHG light 110 may be achieved in acompact manner.

Further, in one or more examples light separation system 200 may furtherinclude a detector 204 downstream of spatial filter 202. For example, incases where light separation system 200 may be a spectroscopy device ora chromatography device, SHG light 110 may be passed through a sample206 positioned between spatial filter 202 and detector 204 formeasurement purposes. However, in one or more examples, light separationsystem 200 may not include a sample 206 and/or detector 126 andassociated components including control unit 132, display unit 134, anduser input receiving unit 136. Thus, light downstream of spatial filter202 may be directed toward a final destination without being passed tosample 130 and/or detector 126.

Turning now to FIG. 3 , FIG. 3 shows a schematic diagram of a thirdexample light separation system 300. Third example light separationsystem 300 is substantially similar to first example light separationsystem 100 with the addition of a third prism 302 positioned downstreamof the second prism 114. The addition of the third prism 302 may furtherspatially separate the SHG light 110 from the fundamental light 112.Thus, even further efficient extraction of the desired SHG light 110 maybe achieved. While third example light separation system 300 does notshow a spatial filter downstream of the third prism 302, the thirdexample light separation system 300 may further include a spatial filterdownstream of the third prism 302, and upstream of detector 126 andsample 130, similarly as in second example light separation system 200.

Moreover, the addition of further prisms and spatial filters may bepossible for an even higher degree of spectral and separation and todirect the desired light beam into preferred direction. However, it isnoted that the addition of further prisms or spatial filters may havediminishing returns as to increased efficiency for extraction of desiredlight.

It is noted that sample 130 and/or detector 126 and associatedcomponents including control unit 132, display unit 134, and user inputreceiving unit 136 may be omitted from the third example lightseparation device, in at least one example. Thus, light downstream ofthird prism 302 may be directed toward a final destination without beingpassed to sample 130 and/or detector 126.

Moving to FIG. 4 , FIG. 4 shows a plot of a percentage of transmissionof SHG light vs. incident angle (θ) 400. The plot 400 shown in FIG. 4corresponds to transmission of SHG light through a single prism atdifferent incident angles (θ), as calculated by ray tracing software. Asshown in FIG. 4 , at an incident angle θ of 30 degrees, transmission ofthe SHG light at p-polarization is approximately 99.7% in the specificexample where the fundamental light is at 440 nm, SHG light at 220 nm,and the prism is made of fused silica. It is noted that plot 402, shownoverlaid onto plot 400, includes indicator lines 404 in dash toillustrate that an incident angle θ of 30 degrees results intransmission of the SHG light of approximately 99.7%.

The plot shown in FIG. 4 is an example where polarization of the sourcelight passed through the prism is in so-called p-polarization. However,it is noted that SHG transmission will be greatly reduced if thepolarization is rotated, or if the incident angle (θ) variessignificantly from 30 degrees in the above example. That is, the SHGtransmission will be greatly reduced if the incident angle (θ) isgreater than 31 degrees or less than 29 degrees and/or the polarizationof the source light is not perpendicular to a base of the prismperforming refraction. The optimal incident angle in conjunction withthe choice of prism tip angle for some specific wavelength can be foundthrough Fresnel equations.

As to fundamental light, transmission of the cross-polarized fundamentallight (in the s-polarization or the transverse-electric mode) has atransmission of about 74%. The major reduction of the fundamental lightdoes not rely on the transmission loss but on the large difference ofthe propagation direction and the subsequent spatial filtering, asdiscussed above.

Turning now to FIG. 5 , FIG. 5 shows a flow chart of an example method500. Method 500 may be carried via a light separation system includingany one or combination of the features as discussed above. Instructionsfor carrying out method 500 herein may be executed by a controller, suchas control unit 132, based on instructions stored on a memory of thecontroller and in conjunction with signals received from sensors of thelight separation system, such as the sensors described above (e.g.,detection unit 126, user input receiving unit 136, and fundamental lightreceiver 138). The controller may employ actuators of the lightseparation system to adjust operation of the light separation system.For example, such actuators may include a display unit such as displayunit 134 and optics 102, according to the methods described below.

Method 500 may begin responsive to receiving a user input at a userinput receiving unit, such as user input receiving device 136. Inexamples where the light separation system may be a spectroscopy device,for example, the user input received at step 500 may be an input requestfor a measurement of a sample. Alternatively, the light separationsystem may be a curing system, and the user input received at step 500may be a user input received via user input receiving unit 136requesting operation of the light separating system for curing purposes.

Responsive to receiving the user input, method 500 may polarize sourcelight at step 502. In particular, polarizing source light at step 502may include polarizing SHG light 504 and polarizing fundamental light506 may be polarized at step 502. Following step 502, method 500 mayinclude directing the polarized source light through a first prism atstep 508. The source light may be a visible source light in one or moreexamples, such as a 430-nm wavelength laser light.

In one or more examples, the polarized source light may be polarized ina direction perpendicular to a base of the first prism, includingpolarization of both the SHG light and the fundamental light in adirection perpendicular to a base of the prism through which the sourcelight is being passed through.

By polarizing the SHG light in a direction perpendicular to a base of aprism through which the SHG light is then passed through, a hightransmission of the desired SHG light may be ensured. For example, asdiscussed above, approximately a 99.7% transmission rate through theprism may be achieved by polarizing the SHG light in a directionperpendicular to a base of the prism through which the SHG light ispassed.

The polarized source light passed through first prism 508 may berefracted such that an exit angle of the desired SHG light differs froman exit angle of the undesired fundamental light. The separated SHGlight may be UVC light emission of approximately 220 nm in wavelength.

However, while the desired SHG light is separated from the fundamentallight following step 508, the separation is insufficient to ensure thatthe extraction of the SHG light is pure, even with a special filterincluded immediately downstream of the first prism. In fact, thefundamental light may have a much larger intensity and has a Gaussianbeam profile. Thus, the inclusion of a spatial filter downstream of thefirst prism may actually lead to diffraction of fundamental lightthrough the spatial filter.

Thus, following step 508, the SHG light separated via refractionperformed by the first prism is further passed through a second prism atstep 510. By refracting the SHG light through the second prism followingrefraction of the SHG light through the first prism, the spatialseparation between the SHG light and the undesired fundamental light maybe further increased, thus providing sufficient spatial separation ofSHG light from the fundamental light for extraction purposes. That is,by passing the source light through the first prism to separate the SHGlight and the fundamental light, and then only pass the SHG lightthrough the second prism without passing the fundamental light throughthe second prism, the technical effect of increased spatial separationbetween the SHG light and the fundamental light may be achieved, thusenabling improved extraction of the SHG light.

Following step 510, method 500 optionally includes passing the SHG lightthrough additional prisms downstream of the second prism. By routing theSHG light through additional prisms after routing the SHG light throughthe second prism at step 510, the SHG light may be even furtherseparated from the fundamental light. Moreover, the use of additionalprisms may beneficially be used to direct the SHG light to a particularlocation.

Continuing with method 500, at step 514 the SHG light may be passedthrough a spatial filter, such as a pinhole, following passing of theSHG light through at least the first and second prism. The inclusion ofthe spatial filter downstream of at least the first prism and the secondprism may help to filter out any fundamental light which may still beproximal the separated SHG light. Further filtering of the fundamentallight out of the SHG light via the spatial filter may be beneficial forthe purposes of improving a purity of the SHG light extracted.

In cases where the light separation system may be a spectroscopy device,method 500 may include passing the SHG through a sample at step 516following passing the SHG light through the spatial filter at step 514.For example, the sample may be a liquid or a gas sample. In someexamples, the sample may be contained within a cuvette.

Following passing the SHG light through the spatial filter at step 514and the sample at step 516, method 500 may include receiving the SHGlight at a detection unit at step 518. However, in some cases the SHGlight may not be passed through a sample between the spatial filter andthe detector. For example, in order to perform a reference reading, SHGlight may be passed directly from the spatial filter to the detectorwithout being passed through a sample for reference purposes. Then,following the reference reading, a sample may be inserted into thedesired SHG light path between the spatial filter and the detector, anda reading of the sample may be taken. Or, in at least one example, areference reading based on detection of the fundamental light may beutilized. Alternatively no reference readings may be utilized in method500.

Based on the SHG light received at the detection unit at step 518 and,in some examples, a reference reading, method 500 may include providinga display at step 520. The display may include a visual data such as agraph showing visualized measured emission peaks, in one or moreexamples. Additionally or alternatively, the display may includequantitative measurement data for the light received at the detectorthat was passed through the sample, such as in the form of a table.Further, in at least one example, the display may include the rawreference measurement data and/or the display may include results frommeasurements that take into account both light received at the detectoras well as reference measurement data. The display at 520 maybeneficially be used to determine information about the sample throughwhich the SHG light has been passed through, such as a chemicalcomposition of the sample, for example.

Alternatively, in examples where the light separation system may not bea spectroscopy or chromatography device, and where the light separationsystem may instead be a curing device or a disinfectant device, forexample, the SHG light may not be passed through a sample and adetection unit following step 514. Rather, in such examples the SHGlight may instead be directed towards surfaces to be cured ordisinfected following step 514. Moreover, such examples may not includea displaying step such as step 520.

Turning to FIG. 6 , FIG. 6 shows a fourth example light separationsystem 600, where a full view of case 206 is shown. As can be seen inFIG. 6 , case 206 includes first compartment 602, second compartment604, and third compartment 606. In one or more examples, compartment 602may include an access point for a user to insert and remove sample 130.For example, a door may be included to allow access for placement andremoval of sample 130. During readings, environmental light is blockedfrom entering first compartment 602 and second compartment 604 toprevent environmental light contamination from skewing reading results.Second compartment 604 may be separated from first compartment 602 toavoid degradation of components contained within compartment 604.

It is noted that control unit 132 is shown in a separate thirdcompartment 606 merely for exemplary purposes and that in one or moreexamples the control unit 132 may be positioned within anothercompartment such as first compartment 602 or second compartment 604. Or,in some examples, control unit 132 may be completely external to thecase. For example, control unit 132 may be wireless connected or have ahardwire connection and be completely separate and external from thecase 206. Moreover, the user input receiving units 134 and the displayunit 136 within third compartment 606 may be accessible by a user toinput requests and to view displays provided via display unit 136. Forexample, the user input receiving units 134 and the display unit 136 maybe positioned on an external surface of the fourth example lightseparation system 600. In other examples, however, one or both of theuser input receiving units 134 and the display unit 136 may becompletely separate and external from the case 206.

Thus, provided herein are systems and methods for efficient separationof light, in particular, polarized UV light. In a first example method,the method may comprise passing polarized source light through a firstprism, the polarized source light including second-harmonic generation(SHG) light and fundamental light, separating the SHG light from thefundamental light, and passing the separated SHG light through a secondprism. Such steps achieve the technical benefit of creating spatialseparation between the desired SHG light and fundamental light, thusenabling extraction of the SHG light for curing, disinfecting,spectroscopy, and sterilizing purposes, for example. Additionally, themethod may further comprise passing the SHG light through a spatialfilter following passing the SHG light through the second prism forfurther filtering of the SHG light from the undesired fundamental light.

In one or more of the example methods discussed above, the fundamentallight is not passed through the second prism, and the fundamental lightis not passed through the spatial filter in order to achieve thetechnical benefit of improved separation between the desired light (SHGlight) and the undesired light (fundamental light). That is, thefundamental light may only be passed through the first prism, in atleast one example.

Additionally or alternatively, one or more of the methods above mayfurther comprise receiving the SHG light at a detector downstream ofboth the second prism and the first prism. For example, in cases wherethe light separation system may be utilized for spectroscopy orchromatography purposes, receiving the SHG light at the detector mayenable measurements to be provided for evaluation purposes. Inparticular, the SHG light may be passed through a sample prior to beingreceived at the detector for spectroscopy or chromatographyapplications.

In a first example system for separating light, the system may compriseoptics providing polarized source light, a first prism positioneddownstream of the optics in a path of the polarized source light, asecond prism positioned downstream of the first prism, the second prismpositioned in a first refracted second-harmonic generation (SHG) lightpath of the polarized source light, and a spatial filter positioneddownstream of the second prism.

In one or more examples, the first example system may further include asecond prism coupled to the first prism. Additionally, in one or moreexamples, the system may comprise a spatial filter positioned in asecond refracted SHG light path of the polarized source light.

As discussed above, in one or more embodiments, additional prisms may beincluded downstream of the second prism. For example, a third prism maybe positioned downstream of the second prism. Further prisms may beincluded in addition to the third prism in one or more examplesdependent upon a direction the SHG light needs to be moved, for example.

In examples where there are three prisms, the spatial filter of thesystem may be positioned in a third refracted SHG light path of thepolarized source light, downstream of the third prism. In examplesystems where there may only be two prisms, a detector may be positioneddownstream of the spatial filter and in a second refracted SHG lightpath, where the second refracted SHG light path is downstream of thefirst prism and the second prism.

In any one or more of the example systems described above, an incidentangle of the source light at the first prism and the second prism may be30 degrees. However, in some examples, the incident angle may range from24.5 to 26.5 degrees or be found by using the Fresnel equations.

In another example light separating system, the system may compriseoptics providing polarized source light, a first prism positioneddownstream of the optics in a path of the polarized source light, asecond prism positioned downstream of the first prism, the second prismpositioned in a first refracted desired light path of the polarizedsource light, and a spatial filter positioned downstream of the secondprism.

Additionally, in one or more examples the system may further comprise acontrol unit, the control unit including instructions stored innon-transitory memory for polarizing source light via optics, anddirecting the polarized source light through the first prism. Forexample, the system may polarize the source light and direct thepolarized source light through the first prism responsive to receiving auser input. The polarized source light may include desired light andundesired light, and wherein the desired light is separated from theundesired light via refraction at the first prism. The desired light maythen be further refracted by the second prism which is positioned in thefirst refracted desired light path. Thus, the technical advantage ofcreating spatial separation between the desired light and the undesiredlight may be achieved via refraction at the first prism and the secondprism. Furthermore, in one or more examples, the system may furthercomprising a detector downstream of the spatial filter, wherein thespatial filter and the detector are both positioned in a secondrefracted desired light path downstream of the second prism. Suchfeatures may beneficially enable accurate measurements to be taken forspectroscopy or chromatography purposes, for example.

Note that the control methods and routines disclosed herein may bestored as executable instructions in non-transitory memory and may becarried out by the control system including the controller incombination with the various sensors, actuators, and other enginehardware. The specific routines described herein may represent one ormore of any number of processing strategies such as event-driven,interrupt-driven, multi-tasking, multi-threading, and the like. As such,various actions, operations, and/or functions illustrated may beperformed in the sequence illustrated, in parallel, or in some casesomitted. Likewise, the order of processing is not necessarily requiredto achieve the features and advantages of the example embodimentsdescribed herein, but is provided for ease of illustration anddescription. One or more of the illustrated actions, operations and/orfunctions may be repeatedly performed depending on the particularstrategy being used. Further, the described actions, operations and/orfunctions may graphically represent code to be programmed intonon-transitory memory of the computer readable storage medium in theengine control system, where the described actions are carried out byexecuting the instructions in a system including the various enginehardware components in combination with the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied tovarious devices utilizing light separation, such as spectroscopy,chromatography, curing devices, and disinfecting devices. The subjectmatter of the present disclosure includes all novel and non-obviouscombinations and sub-combinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1-6. (canceled)
 7. A system for separating light, comprising: opticsproviding polarized source light; a first prism positioned downstream ofthe optics in a path of the polarized source light; a second prismpositioned downstream of the first prism, the second prism positioned ina first refracted second-harmonic generation (SHG) light path of thepolarized source light; and a spatial filter positioned downstream ofthe second prism.
 8. The system of claim 7, wherein the second prism iscoupled to the first prism.
 9. The system of claim 7, wherein thespatial filter is positioned in a second refracted SHG light path of thepolarized source light.
 10. The system of claim 7, further comprising athird prism positioned downstream of the second prism.
 11. The system ofclaim 10, wherein the spatial filter is positioned in a third refractedSHG light path of the polarized source light.
 12. The system of claim11, wherein the spatial filter is further positioned downstream of thethird prism.
 13. The system as in claim 7, wherein an incident angle ofthe source light at the first prism and the second prism is based on amaximum transmittance according to Fresnel equations.
 14. The system asin claim 7, further comprising a detector downstream of the spatialfilter and in a second refracted SHG light path.
 15. The system as inclaim 14, further comprising a sample positioned between the spatialfilter and the detector. 16-20. (canceled)